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May 23, 2012

Options to Cut Inspection Time

We are forced to correct many solder defects on the PCB bottom side (SMD glue side). The inspection and search for defects is taking too long. Our soldering waves are not new, we have tried several times to prevent these defects, but with old equipment we are limited.

Would you suggest we investigate a 3D AOI system to save inspection time? Any other suggestions?


Experts Comments

Automated inspection is amazingly fast and accurate. It enables you to get the data you need.
Lee Levine
President, Consultant
Process Solutions Consulting Inc.
Lee Levine has been a Process Engineer and Metallurgist in the semiconductor industry for 30 years. He now operates his own company Process Solutions Consulting Inc where he consults on process issues and provides SEM/EDS and metallography services.
The key issue is not to decrease inspection time, but to reduce your defects that you are experiencing in your wave solder process. Without knowing the types of defects that you must repair, I would suggest that you investigate the use of nitrogen inerting for your wave solder process. In my past and present experience the reduction of many types of defects, such bridging, icicles, and insufficient solder can be reduced by using an inert atmosphere. Some added benefits are dross reduction, that may be a cause for your defects and the reduction of flux required per board. Reduction in time to repair the defects, increased productivity and material costs = overall cost savings. We offer a retrofit inerting kit to introduce nitrogen to the solder pot and wave area.
Gregory Arslanian
Global Segment Manager
Air Products & Chemicals, Inc.
Mr. Arslanian has been involved in electronics packaging processing and equipment since 1981 including flipchip, TAB, wirebonding and die attach. Current responsiblities include R&D, applications, marketing and customer interaction.
Without much more knowledge of your situation, my gut reaction would be to say "no." It's almost always better to invest in preventing defects than in inspection and repair. That said, it may be that you have designs that you are not in control of (customer design) and the design may be a big contributor to the defects you are seeing.

The first step to solving this is to figure out the root causes - why does each specific defect type happen? Is it mainly because the design is difficult or deficient, or mainly because the soldering equipment is incapable? If the former, and you have no control over the design, then inspection may be the only avenue. If the latter, then you can consider upgrades to the equipment to eliminate the defects.

Only after you have exhausted all resources to understand the root causes of the defects and eliminate as many of them as possible should you consider investments in automated inspection. Remember that the initial cost of AOI is not the only cost. You will also be faced with the cost of programming, which may be substantial. You will also be dealing with some level of "false positives" which will be an ongoing cost that must be minimized by optimization of programs.

The big up-side to AOI is that it is very efficient, unlike manual inspection which will inevitably miss as many as 30% of defects. AOI also allows you to more easily log defects into an SPC system, which can lead to much faster, easier identification of root causes.
Fritz Byle
Process Engineer
Fritz's career in electronics manufacturing has included diverse engineering roles including PWB fabrication, thick film print & fire, SMT and wave/selective solder process engineering, and electronics materials development and marketing. Fritz's educational background is in mechanical engineering with an emphasis on materials science. Design of Experiments (DoE) techniques have been an area of independent study. Fritz has published over a dozen papers at various industry conferences.
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